Communication and Homeostasis

Outline the need for communication systems within multicellular organisms, with reference to the need to respond to changes in the internal and external environment and to co-ordinate the activities of different organs.

Organisms need to respond to external stimuli, e.g. temperature, oxygen concentration and levels of sunlight. These may be over time, e.g. winter fur to summer fur, or quickly, e.g. changing size of pupils.

Internal environments change too- the build up of carbon dioxide as a result of respiration changes the pH of the tissue fluid, and therefore inhibits enzyme activity. Multicellular organisms need to coordinate different organs, so this requires a good communication system which will:

• Cover the whole body

• Enable cells to communicate with each other

• Enable specific communication

• Enable rapid communication

• Enable both short and long-term responses.

State that cells need to communicate with each other by a process called cell signalling.

State that neuronal and hormonal systems are examples of cell signalling.